Cursory googling says tetra is Greek and perfect is Latin, so its a bastard word like erogenous or television.

Side point: television is a bastard word, but erogenous is not Greek eros + Latin genus; it's all greek (ἐρωτογενής — it would be erotogenous in English since the root of the word eros is erot- , but the extra syllable was dropped; another example of differentiated transliteration is φωτογενής which became photogenic instead of photogenous).

I have just written an essay about the word water in the sibling post comments.

One thing I discovered in the process is that the word water comes to english all the way from Proto Indo European. The word hydro, however, comes from ancient greek, which comes from the same PIE word for water.

> bastard word like ... television.

From where I am, it is simply telly, because why not bastardise it some more while we are at it.