Aha, so the root is not directly 밀(mil, “water”) + possessive infix -s- outright, but at least a root of 믯(muys, “*slippery”), derived from 밀(mil, “water”).
For the latter portion, 글(geul) as just an "affix" seems quite vague. There's the clear example shown in 그립다(geuripda) with adjectivizing infix -b-, and a lack of clarity in the Mac dictionary. Are there other qualitative verbs that end in 그럽다? ‑‑ Eiríkr Útlendi │Tala við mig06:57, 23 August 2016 (UTC)Reply
글 seems to be an ideophone (擬態語) suffix. There are a lot of adjectives ending in 그럽다:
Really interesting possibility; the origin of —글— (-geul-) seems obscure, but a relationship with 그 (geu) is possible. 그럽다 would be analysed as 글 (geul) (which can be either part of the root or an affix) + —업— (-eop-, adjectival suffix). I had a look in the Middle Korean reference books I have and could not find any reference to the root-forming element —글— (-geul-). It seems to me that —글— (-geul-) could be a long-obsolete ideophone suffix, which gave rise to Middle Korean 擬態語 roots 징글 (jinggeul), 믯글 (muitgeul), 너글 (neogeul) (< 넓— (neol-)), 시끌 (sikkeul), to which —업— (-eop-, adjectival suffix) was added to produce the modern —그럽다 words. Some evidence for the ideophonic nature of these roots is in the expressive adjectives:
And the common *ku in the allofam may be related to 그 (geu).
P.S. Seo considers the kur(i) in 미꾸라지 (mikkuraji, “loach”) and its ancestor 믯구리 (muitguri) to be related to 개구리 (gaeguri, “frog”) and 머구리 (meoguri, “frog”). I'm not very convinced. Wyang (talk) 04:39, 24 August 2016 (UTC)Reply