The "unicode" program (in Ubuntu's package repository) gives the Unicode entry for any character:
$ unicode ℘
U+2118 SCRIPT CAPITAL P
UTF-8: e2 84 98 UTF-16BE: 2118 Decimal: ℘ Octal: \020430
℘
Category: Sm (Symbol, Math); East Asian width: N (neutral)
Unicode block: 2100..214F; Letterlike Symbols
Bidi: ON (Other Neutrals)
Age: Assigned as of Unicode 1.1.0 (June, 1993)
If you already have a copyable version of the character it also works in the original Google search. Or any other place you can put it. The problem is when you don't have the literal character as text (say, an image, video, or non-digital source) and need to reproduce it to do that lookup in the first place.
