後是

Noun

 * 1) back, rear
 * 2) later (times), afterwards
 * 3) (possibly, proper noun evidence only) north
 * 1) (possibly, proper noun evidence only) north

Reconstruction notes
Although obscured by the logographic nature of the orthography, the Old Korean stem for "back; afterwards" (or at least its earlier form) is believed to have been disyllabic. The Middle Korean reflex has a bimoraic rising tone, which is the result of a merger of a low-pitch and high-pitch syllable. In particular, rising-tone stems ending in the glide are often the result of an intervocallic consonant being elided before.

One of the has an element phonographically spelled, with the apparent meaning of "north". If this is to be connected to, one of whose meanings is "north", the lost consonant may have been.

The Middle Korean reflex has a final which may be the remnant of an ancient place-related suffix  (see Appendix:Middle Korean h-final nouns). This is either absent in the interpretative gugyeol corpus, or possibly incorporated with the locative ending, as the word mainly occurs in the locative case as (*TWUyk-uy).