3 letters · 6 points in Scrabble
originMost likely from the intrusive R, between "yeah" (/jəː/) and a non-high vowel (/ə/, /ɪə/, /ɑː/, /ɔː/). For example, "Yeah-r-I know" (/jəɹ ʌɪ nəʊ/).
Etymology from Wiktionary, CC BY-SA 3.0