Per Vasmer, borrowed from Iranian language, based on the appearance of /r/ in place of /l/; cognate with Old English molda (“head”), Ancient Greek βλωθρός (blōthrós, “lifted up, high”), Sanskrit मूर्धन् (mūrdhán, “forehead, head, apex”), Avestan 𐬐𐬀-𐬨𐬆𐬭𐬆𐬜𐬀 (ka-mərəδa, “head”). See Proto-Indo-Iranian *mr̥Hdʰā́. Possibly connected with synonymous Armenian մռութ (mṙutʻ). Alternatively a deverbal from *mъrdati (“to wag, to wiggle”).
*mъrda f
singular | dual | plural | |
---|---|---|---|
nominative | *mъrda | *mъrdě | *mъrdy |
genitive | *mъrdy | *mъrdu | *mъrdъ |
dative | *mъrdě | *mъrdama | *mъrdamъ |
accusative | *mъrdǫ | *mъrdě | *mъrdy |
instrumental | *mъrdojǫ, *mъrdǫ** | *mъrdama | *mъrdami |
locative | *mъrdě | *mъrdu | *mъrdasъ, *mъrdaxъ* |
vocative | *mъrdo | *mъrdě | *mъrdy |
* -asъ is the expected Balto-Slavic form but is found only in some Old Czech documents; -axъ is found everywhere else and is formed by analogy with other locative plurals in -xъ.
** The second form occurs in languages that contract early across /j/ (e.g. Czech), while the first form occurs in languages that do not (e.g. Russian).