liar vs fibber

liar and fibber both are nouns.

Word	Noun	Adjective	Verb	Adverb
liar	Yes	No	No	No
fibber	Yes	No	No	No

As nouns, fibber is a hyponym of liar; that is, fibber is a word with a more specific, narrower meaning than liar:

Other hyponyms of liar include false witness, perjurer, fabricator, storyteller.

liar (noun)	fibber (noun)
a person who has lied or who lies repeatedly	someone who tells lies