From Old High German stih, from Proto-Germanic *stikiz. Cognate with German Stich, Dutch steek, English stitch. Luxembourgish -a- is regular. The plural Stéch shows the umlauting influence of the suffix -i in Old High German stihhi (at the time probably pronounced [stɪx] vs. [stixːi]). Compare Schratt, Strack, and strong verbs like schwammen → schwëmmt.