"a kiss," 1560s; probably of imitative origin, as are Welsh and Gaelic bus "kiss, lip," French baiser "kiss" (12c., from Latin basiare), Spanish buz, German dialectal Buss, Turkish bus, Persian busa, Hindi bosa.
"to kiss," 1570s, from buss (n.). Related: Bussed; bussing.
Kissing and bussing differ both in this,
We busse our wantons, but our wives we kisse.
[Robert Herrick, "Hesperides," 1648]