What did Xin mean in ancient times?

Xin, the original meaning of word-making, noun: a knife that tattooed slaves or criminals in ancient times. The original meaning only exists in ancient Chinese.

Xin is very hurt. -Biography of the White Tiger

Part of speech is extended to adjectives: sharp and irritating, unbearable.

There is bitterness in bitterness and sweetness in sweetness. -"Chu Ci"? call

Part of speech is extended to ordinal number: the eighth place in heavenly stems, which is in line with the time of earthly branches.

Its day is Geng Xin. -The Book of Rites? Monthly order