'openbill' originates from English as a compound of 'open' + 'bill', literally describing a bill (beak) that is open or has a gap.

'openbill' developed from earlier descriptive uses such as 'open-billed' or the phrase 'open-billed stork' and was later used as a noun name for the birds (e.g., 'openbill').

Initially it described the physical condition 'having an open (or gapped) bill', and over time it became used as a noun naming the stork species and, in separate usage, to describe an 'open bill' (an unpaid account).