-some [səm] suffix
[Sense: 1; Origin: Old English -sum]
[Sense: 2; Origin: some]
1.) [in adjectives]
tending to behave in a particular way, or having a particular quality
a troublesome boy (=who causes trouble)
a bothersome back injury (=that bothers you)
2.) [in nouns]
a group of a particular number, for example in a game
a golf foursome (=four people playing golf together)

Dictionary of contemporary English. 2013.