Not only a primitive, but actually a kanji (and a quite common one at that). I think it's a much better mnemonic as lack or yawn than as "bound up person" (and as Pangolin pointed out, it doesn't actually contain the "bound up" primitive anyway).
Incidentally, the word "yawn" (あくび) can be written as 欠 or 欠伸 (lack stretch). Apparently 欠 derives from a pictograph of someone opening their mouth and it occurs in kanji related to opening one's mouth (e.g. 歌). You can see more about this character (and some cute pictures of furry animals yawning) at this page (Japanese):
http://wpedia.search.goo.ne.jp/search/%A...ind=epedia
Incidentally, the word "yawn" (あくび) can be written as 欠 or 欠伸 (lack stretch). Apparently 欠 derives from a pictograph of someone opening their mouth and it occurs in kanji related to opening one's mouth (e.g. 歌). You can see more about this character (and some cute pictures of furry animals yawning) at this page (Japanese):
http://wpedia.search.goo.ne.jp/search/%A...ind=epedia