single-handed adj.

early 14c., "unmarried," from Old French sengle, sangle "alone, unaccompanied; simple, unadorned," from Latin singulus "one, one to each, individual, separate" (usually in plural singuli "one by one"), from PIE *semgolo‑, suffixed (diminutive?) form of root *sem- (1) "one; as one, together with."

The meaning "consisting of one unit, individual, unaccompanied by others" is from late 14c., often merely emphatic. The meaning "undivided" is from 1580s. Single-parent (adj.) is attested from 1966.

in compounds, "having hands" (of a certain type), mid-14c., from hand (n.). Related: -handedness; -handedly.