>Szukałem w kilku słownikach, oczywiście nie znalazłem czegoś takiego
Dictionary.com Unabridged (v 1.0.1) - Cite This Source
cheer‧er-up‧per [cheer-er-uhp-er] Pronunciation Key - Show IPA Pronunciation
–noun Informal.
a person or thing that cheers a person up: A good joke is the best cheerer-upper.
[Origin: cheer up + -er1, joined pleonastically to both v. and particle]
Ju has to try harder, Juhas ;)