Oettinger Norbert. Der Flexionsyp idg. *sḗh2-ṷr̥ ‚saure Flüssigkeit‘, *nḗbh-s n. ‚Gewölk‘

Indogermanische Forschungen. — 2015. — Vol. 120. — 255-268.Abstract: Lengthened grade of root syllables in PIE words was either motivated or came about by analogy. The adjective *sh₂ur-ó- > *suh₂ro- > *sūro- ‘sour and liquid’ is derived from *sḗh2-ṷr̥ n. ‘sour fluid’ (> Hitt. šēḫur ‘urine’). Here the motivation of the lengthened grade can be guessed: Cuneiform Luvian šiḫuwa- ‘sharp, acid’ < *sēh₂ṷo- can be explained as vṛddhi derivation from an earlier *séh₂-u- ‘sourness, sharpness’. The noun *sḗh₂-ṷr̥ has probably been derived from *sēh₂ṷo-. Hieroglyphic Luvian tipas ‘sky, heaven’ is best derived from a neuter s-stem *nḗbʰ-s n. ‘cloud(s)’. Probably there was an early PIE paradigm *nḗbʰ-s, gen. *nébʰ-s-s, whose genitive was soon replaced. Here we cannot know the motivation of the lengthened grade but it is likely that it was there. In consideration of this neuter stem *nḗbʰ-s it may well be that also the much disputed Old Irish word síd ‘fairy mound, peace’ goes back to a lengthened grade neuter s-stem *sḗd-s ‘domicile, seat’. The suffixal e-grade of neuter nouns in *-es/-os stems from the locative of the acrostatic type *nḗbʰ-s.
Keywords: s-Stämme, akrostatisch, Langstufe, Derivation, Hethitisch, Luwisch, Altirisch