'serif' probably originates from Dutch, specifically the word 'schreef,' where 'schreef' meant 'line' or 'stroke'.

'serif' entered English printing usage in the late 18th to early 19th century from printers' jargon; the Dutch/Middle Dutch 'schreef' (meaning a written line or stroke) was adapted into English typographic terminology and eventually became 'serif'.

Initially it referred generally to a 'line' or 'stroke'; over time the meaning narrowed to the small finishing stroke on letters and then extended to denote typefaces that have such strokes.