From Proto-Vietic *ʔəh (“to stay”); cognate with Muong ớ.
Most prepositions in Vietnamese were originally verbs: cho (“to give; for”), đến (“to come; to”), tới (“to arrive; to”), lên (“to go up; onto”), vào (“to enter; in, into”), theo (“to follow; according to”), về (“to return; about”).
Similarity to Chinese 於 is coincidental, as semantically the Vietnamese word is a grammaticalized verbal and phonetically there is a tonal mismatch.
- at, in
ở • (於, 𣄒, 𫵦)
- to be, to live, to stay, to remain