The word 'swig' first appeared in English in the mid-16th century. Its origin is uncertain but it is widely regarded as an imitative or expressive creation, possibly echoing the sound of liquid being gulped or swilled in the mouth and throat. This formation follows a common pattern where words for drinking actions are derived from sounds associated with them. The word has retained its core meaning related to drinking in large gulps from its earliest recorded use to the present day.

This word is considered a simplex form. It is likely an onomatopoeic or expressive formation in English, imitating the sound or action of swallowing liquid.