What is the uncontracted form of "κεῖμαι"? (Greek)

Question

I got this word κεῖμαι while trying to learn ὑποκείμενον, found in this answer to another question.

All the deponent verbs I've run across so far had an ο for theme vowel, as in: βούλομαι or φαίνομαι. Contraction resulted in an ω (as in θεᾰ́ομαι to θεῶμαι) or ου (ἡγέομαι to ἡγοῦμαι).

In general, I have not seen ο "losing" to another vowel (e.g. α or ε) in a combination and disappearing. For example, α + ο = ω, ε + ο = ου, and ο + ε = ου. To wit, ο survives.

I thought of two possibilities.

1. κεῖμαι never had an ο. For example, it comes from κέεμαι.

2. κεῖμαι came by a strange sort of contraction from κέομαι.

Please tell me what is going on, and if possible provide other verbs that behave like κεῖμαι.

I believe a similar question arises in respect of ὑποκείμενος. So far I have only seen -μενος with α or ο for a theme vowel (as in πεμψάμενος or πεμπόμενος) or without a theme vowel (as in πεπεμμένος). Contraction might give me ου (as in οἰκούμενος). But how do we end up with ει in ὑποκείμενος? Thanks.

Answer 1

The verb κεῖμαι isn't a contract verb like θεάομαι or ἡγέομαι (or a 'regular' verb like λύω); it's an athematic verb like τίθημι, δίδωμι, or ἵημι, but deponent. So, the circumflex isn't showing contraction as it is in θεῶμαι and ἡγοῦμαι; it's used simply because the accent is on the penult, the penult is a long syllable, and the ultima is short, per the regular rules for accent.