Reconstruction:Proto-Slavic/strьmь

Not entirely clear, but the presiding opinion tends towards an archaic i-stem from Proto-Indo-European *(s)ter- (“rigid, erect”) or *(s)terh₁- (“to stiffen”)[1] + *-ьmь (compare o-stems *-ьmъ, *-ьmo), related to Ancient Greek στερεός (stereós), στέριφος (stériphos, “solid, rigid”), στερέμνιος (sterémnios, “sturdy”), German stramm (“tight”). Sobolevsky, Mladenov have alternatively proposed possible derivation from Proto-Indo-European *srey- (“to flow, stream”) akin to Proto-Slavic *struja, *strumy (“stream”).

Machek further suggests possible kinship to Lithuanian trìmti (“to shiver”) (also meaning “to sink, to subside”), trem̃ti (“to exile”) < Proto-Indo-European *trem-.

*strьmь

1. steep, abrupt

   Synonym: *krǫtъ

• *strьmъ (o-stem)
• *strьmьnъ (extended with no-stem)

• *strьměti (“to obtrude, to be steep”), *strьmiti (“to strive”)
• *strьmьcь (“striver”)
• *strьmina (“steepness”)
• *strьmьgolvъ, *strьmogolvъ (“headlong”)

• *stremę (“stirrup”)
• *stromъ (“steep slope, cliff”)
  • *stromъ, *stromъkъ (“steep”)
• *trьmъ (“solid”)
  • *trimati (“to keep”)

• South Slavic:
  • ⇒ Bulgarian: стръм f (strǎm, “steep”) (poetic, fosilized substantivized form)

*strьmь

1. exactly, absolutely

• South Slavic:
  • Old Church Slavonic: стрьмь (strĭmĭ)

• Todorov, T. A., Racheva, M., editors (2010), “стръм”, in Български етимологичен речник [Bulgarian Etymological Dictionary] (in Bulgarian), volumes 7 (слòво – теря̀свам), Sofia: Prof. Marin Drinov Pubg. House, →ISBN, page 512
• Vasmer, Max (1964–1973) “стреми́ть”, in Oleg Trubachyov, transl., Этимологический словарь русского языка [Etymological Dictionary of the Russian Language] (in Russian), Moscow: Progress
• Melnychuk, O. S., editor (2006), “стрім”, in Етимологічний словник української мови [Etymological Dictionary of the Ukrainian Language] (in Ukrainian), volumes 5 (Р – Т), Kyiv: Naukova Dumka, →ISBN, page 445