early 15c., earlier servitute (late 14c.), "slavery, bondage, condition of being enslaved," from Old French servitude, servitute (13c.) and directly from Late Latin servitudo "slavery," from Latin servus "a slave" (see serve (v.)) + abstract noun suffix (see -tude). Also "state of being a feudal vassal" (c. 1500). The meaning "compulsory service or labor," such as a criminal undergoes, is by 1828.
Other words in similar senses, many obsolete, include servantship "state or condition of being a servant" (1570s); servage "servitude, bondage, slavery; serfdom, subjugation, feudal homage to a ruler" (c. 1300, from Old French servage and directly from Medieval Latin servagium); servity "slavery, servitude" (late 15c., from Latin servitus).