Literally: interest – flavor – harbor – harbor
Alternately: Being intensely interested in something. Overflowing with endless enthusiasm. Alternately, a descriptor of the interesting thing.
Notes: 興味, by itself, refers to curiosity about or interest in something. 津… is weird. It “means” something like a harbor, but has at times been used as an associative particle, as in 国津神 (kuni-tsu-kami, “gods of the land”), and in this case refers to liquid pouring or gushing out. The doubling strengthens the term, so today’s compound might be literally translated as something like “gushing with interest.”
Apparently some people replace 津 with homophone 深, but this is considered incorrect. It’s okay, though, to use the doubling mark 津々 instead of writing out the same kanji twice in a row.
Super interesting… like this fishy!