I'm not sure if this is just a coincidence, but there's two related words:
- 只得 (zhǐdé) = "be obliged to"
- 得 (děi) = "to have to"
They have similar meanings, and share the character 得 (although with different pronunciation). It seems like they may be etymologically related.
Question: Is there an etymological connection between 只得 (zhǐdé) and 得 (děi)?
I wouldn't know where to begin investigating this, but Googling
只得 得 didn't help.