Thieves, as in Ali Baba and the forty thieves.
Baseball teams can have 40 players.
Winks - to sleep is to catch 'Forty winks"
Soda comes in groups of 6
dogs
Pennies
states
what comes in groups of 12
Arms, legs.
rugby teams
Case of beer
gaggle of geese
Inches in a foot
scorpion legs
Pennies