unerringly

If it is what I think it is, the word stems from error so unerringly - un-error without error, without mistakes.

SYNONYMS:.....unerringly=trustworthy impeccable infallible reliable certain perfect exact

unerringly - un hearing means he will not make mistake.

Unerring (making no mistakes), Stumbling (making mistakes, mainly while speaking).

unfiegn: un (not)+ feign is like "pain", feign means pretend, if you feign infornt of someone who admires you it give them a great pain, try to be genuine to them