This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development is uncertain. 鯳 combines 魚 (fish) with 底 (bottom), but the original purpose and meaning are unclear.
The fish radical 魚 beside 底 (bottom) suggests a fish associated with the bottom, but the exact meaning is unclear.
For テイ, imagine a fish at the bottom of the sea, and you take a tea break watching it: tea -> テイ.