のなんのってSo much that, Extremely, Very

のなんのって is a casual phrase that is used in spoken Japanese to indicate that the word before it is 'excessively (A)', or 'extremely (A)'. This structure consists of the case marking particle の, the pre-noun adjectival 何(なん)の 'what kind of', and って, an abbreviation of という 'to say'.

The literal meaning of 'and to say it's (A) or something' just indicates that something is so (A) that if it is not that then the speaker doesn't know what to call it.

This structure will be seen after い-Adjectives, な-Adjectives followed by な, and verbs.

のなんのって itself is a more condensed variation of ～の～ないのって, which has the same meaning, but has (A) appear in both the positive and negative for 'to say it's (A) or not (A), (B)', where (B) will usually be a phrase explaining the extent of (A). Occasionally (B) will be left unsaid, as ～の～ないのって itself is always used to mean 'extremely (A)'.