Is it ensure, insure, or assure?
"one who or that which snaps," 1570s, agent noun from snap (v.). Applied to various fishes since 1690s. Slang meaning "vagina" is by 2000. As a short form of snapping turtle (1784) it is recorded from 1872. Snappers "teeth" is attested from 1924.
To insult, esp publicly and in a sort of competitive way: After Ivey spent five minutes on stage snapping on a white man in the audience, they conducted snapping sessions to get contributions from professionals
[1990s+; the general sense is found by 1578, but the current use is probably not a survival]