bedfellow

noun

1. Also called bedmate. a person who shares one’s bed.
2. an associate or collaborator, especially one who forms a temporary alliance for reasons of expediency: Politics makes strange bedfellows.

noun

1. a person with whom one shares a bed
2. a temporary ally or associate

n.

“close friend, roommate,” mid-15c., from bed (n.) + fellow (n.). Also (late 15c) “concubine.” Earlier in the “close companion” sense was bed-fere (early 14c.). Bedsister “husband’s concubine” is recorded in Middle English (c.1300).