Where does “dad shower” come from?

dad shower (English) comes from English baby shower, from English baby, from Middle English baby, from Middle English -y, from Old English -iġ, from Proto-West Germanic -g, from Proto-Germanic -gaz, from Proto-Indo-European -ḱos — -y, -ic.

Ancestry of “dad shower”, step by step

dad shower traces back through two separate lines of ancestry.

via English baby shower

StepLanguageWordMeaning
1Englishbaby showerA party celebrating the pending or recent birth of a child, involving guests giving gifts (typically babycare items) to the parent(s)
2EnglishbabyA very young human, particularly from birth to a...
3Middle EnglishbabyA child or baby
4Middle English-yDesignates an adjective, in many cases formed by...
5Old English-iġ-y, -ic
6Proto-West Germanic-gForms adjectives from nouns and verbs with a...
7Proto-Germanic-gaz-y
8Proto-Indo-European-ḱos-y, -ic

via English dad

StepLanguageWordMeaning
1EnglishdadA father, a male parent; Synonyms: dada, daddy,...
2EnglishDade
Every word from Proto-Indo-European -ḱos