From Wikipedia:

Forty-Fives (also known as Forty-Five, Forte Fives, Auction Forty-Fives, Auction 120s, 120, Growl, Spoil Five, Maw and Strong Fives) is a trick-taking card game that is played in Ireland, and in some parts of New England, New Brunswick, Prince Edward Island, and Nova Scotia where it is known as Forte Fives. It is closely related to the game One-hundred and ten (110) also described below.

The game may have got its name from "forte" which is Latin for strong which describes the 5's in the deck. The origin of this game is thought to be Ireland.[citation needed] In the 1920s, the game became Forte Fives when it moved South into the Merrimack Valley of Massachusetts and New Hampshire with French Canadian immigrants. Today, Forty-fives continues to be very popular in the Merrimack Valley. It is played with a standard deck of 52 cards (sometimes with jokers).


Taken from the Article: 45s - Merrimack Valley’s Original Card Game - as published in Merrimack Valley Magazine:

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So much about the card game forty-fives doesn’t add up.

If in the right suit, the 5 is the best card, a jack beats a king, and a 2 can be better than a 10 … but only when it wears black. For the uninitiated, it just gets more confusing from there.

Even the name of the game is ambiguous. Some say the name forty-fives refers to the four 5s in the deck, others say it has to do with a Canadian version of the game, in which the goal is to reach 45 points (the Canadians call our version “120”). Then there’s the theory that forty-fives is derived from “forte” — meaning strong — the 5 being the “mightiest” card. And is it written “45s,” or “forty-fives”?

Through all the confusion, however, it all makes sense to legions of forty-fives players around the Merrimack Valley. A game rooted in 19th century Ireland, forty-fives is as popular as ever across the Valley in 2012, whether it’s played for fun, in a league, at a fundraiser or even on a computer.

The following rules summary was taken from www.the45scardgame.com

Rules (Merrimack Valley Style)

Objective: Partners try to win tricks and prevent their opponents from doing so. The first team to reach 120 points wins the game.

Scoring: Each trick counts for 5 points, and the highest trump in play is an additional 5. After the hand, each team counts what they have taken. If the bidder's team has taken at least the amount of their bid, they score all they have won. If this team fails, the amount of their bid is deducted from their score. The other team in either case always scores what it has won in tricks.

Winning the Game: The team to first reach a total of 120 points wins the game. If both teams reach 120 in the same hand, the bidding team wins the game.

Players: This game can be played with anywhere from 2 to 10 players, but in this version it's 2 vs. 2 (partners).

Cards: A regular deck of 52. The highest trump is the 5, then the Jack, then and Ace of Hearts (no matter what suit is trump). After that it goes Ace of suit, King, Queen, and then it black it goes 2 through 10 and in red 10 through 2 (both
cases skipping the 5).

The Full rank in the trump suit is the following;
From highest to lowest:

Hearts:
5, J, A, K, Q, 10, 9, 8, 7, 6, 4, 3, 2

Diamonds:
5, J, Ace of Hearts, A, K, Q, 10, 9, 8, 7, 6, 4, 3, 2

Clubs:
5, J, Ace of Hearts, A, K, Q, 2, 3, 4, 6, 7, 8, 9, 10

Spades:
5, J, Ace of Hearts, A, K, Q, 2, 3, 4, 6, 7, 8, 9, 10

The Full rank in off suit is as follows: (the Ace of Hearts is not shown since it is always a trump and always the third highest card);

From highest to lowest:

Hearts:
K, Q, J, 10, 9, 8, 7, 6, 5, 4, 3, 2

Diamonds:
K, Q, J, 10, 9, 8, 7, 6, 5, 4, 3, 2, A

Clubs:
K, Q, J, A, 2, 3, 4, 5, 6, 7, 8, 9, 10

Spades:
K, Q, J, A, 2, 3, 4, 5, 6, 7, 8, 9, 10
Dealing: Each player is dealt 5 cards in batches of 3 then 2. After the initial 3 cards to each player, 3 are dealt to a kitty followed by 2 more to each player.

Bidding: The bidding starts with the player to the left of the deal and continues clockwise. Each player in turn may either
bid or pass. Bids are made in multiples of 5 up to 30, with the minimum opening bid being 15. No suit is mentioned during
the bidding process until all bids have been made. The highest bidder names the trump suit.

Drawing: Each player discards as many cards (up to 4) as he wishes from his hand. The dealer then restores each player's
hand to 5 cards, starting with the player to his left. Cards are dealt all at once to each player (no 3-2 method).

Playing: The bidder makes the opening lead. The hand is played out in 5 tricks. If a trump is lead and you have any trump
cards, you must follow suit.* If an off-suit card is led, any card may be played. A trick is won by the highest trump or the highest card of the suit led if no trump are played.


Reneging exception: The three highest trumps (5, J, Ace of Hearts) have the privilege of reneging when a lower trump is led. For example, if the trump 6 is led, a player holding any of these three top trumps without lower trumps may throw off-suit instead of following suit (if he has lower trump also, then he must play a trump). But there is no reneging a higher trump. For example, if the trump Jack is played, the holder of the 5 may renege, but not the holder of the Ace of Hearts.