unexpectedly; actually; to go so far as to; indeed
Depicts a tattoo tool (辛) marking a person's (人) head as punishment for a crime. Based on the original meaning "tattoo criminals on the face", now written as 黥. The current meaning is a phonetic loan.
《說文》：“竟，樂曲盡為竟。从音，从人。”
tattoo criminals on the face