c. 1200, sikenen, "to become ill," from sick (adj.) + -en (1). Transitive sense of "to make sick, affect with illness" is recorded from 1610s. Related: Sickened; sickening. The earlier verb in Middle English was simply sick (Old English seocan) "be ill, fall ill." It is attested by 1825 as "affect with loathing or disgust."