This etymology is missing or incomplete. Please add to it, or discuss it at the Etymology scriptorium. Particularly: “Nôm character are not very indicative of whether the ‹r-› was inherited (i.e. it's from *r) or is the result of spirantization (< medial *-s-). The phonologically shape (‹-ao› + a C tone) is not very common for native words, so this is more likely a loanword.”