Английский Этимологический словарь - stroke (n.)

- "act of striking," probably from O.E. *strac, from P.Gmc. *straikaz, related to the verb stracian (see stroke (2)). The meaning "mark of a pen" is from 1567; sense in stroke of genius first found 1672; the meaning "single pull of an oar or single movement of machinery" is from 1731. Meaning "apoplectic siezure" is from 1599. Swimming sense is from 1800.