honest-to-goodness

[on-ist-tuh-goo d-nis] /ˈɒn ɪst təˈgʊd nɪs/
adjective
1.
real or genuine.
adverb
2.
really, truly, or genuinely.
Also, honest-to-God
[on-ist-tuh-god] /ˈɒn ɪst təˈgɒd/ (Show IPA)
.
Origin
1915-20
Idioms and Phrases with honest to god

honest to God

Also, honest to goodness or Pete; honest Injun. Truly, really, as in Honest to God, I didn't know it was yours, or Honest to goodness, we had exactly the same experience, or I promise I'll finish in time, honest to Pete, or Honest Injun, I didn't take your wallet. These colloquial assertions date from about 1900, except for honest Injun, dating from the late 1800s and today considered offensive.