steyg-
“to stride, to climb”climb, step, stride
Root for climbing/stepping, yielding English stair, stile, stirrup, Greek steikhein.
Discussion
The PIE root *steyg- (to stride, to step, to climb) produced vocabulary for upward movement and measured progression across multiple branches.
English stair (OE stǣger, from PGmc *staigriz) continues the root natively — the stair as a stepped ascent. The related stile (OE stigel, a stepped crossing over a fence) and the archaic sty ("to climb") preserve the basic climbing sense. German steigen (to climb, to rise) and Steig (a steep path) are the transparent cognates.
Greek steíkhein (στείχειν, "to walk in rows, to march in formation") preserves the root with a subtly different emphasis — not climbing but ordered stepping. The derivative stíkhos (στίχος, "a row, a line, a verse of poetry") gave English stich (a line of verse) and distich (a couplet — two lines). The concept of verse as measured stepping is also found in *ped- (foot), since metrical "feet" are the stepped units of poetry.
The already-treated *steyǵʰ-mn̥- (id 1377) covers the nominal derivative in more detail, including the stirrup connection (German Steigbügel, "climbing-bow").
The root occupies a specific niche in the PIE motion vocabulary: where *gʷem- meant "to come/arrive" and *h₁ey- meant "to go," *steyg- specifically meant upward movement — climbing, ascending, mounting. This specialisation implies terrain that required vertical locomotion.
Notes
Pokorny 1017. English stair, stile, stirrup (stig-rap: climbing rope).