Not from a baby, you monster
(Ocha no ko saisai; “Alright; tea candy!”)
Something super simple and easy; just a little thing. Words of encouragement. Something as effortless as picking up and eating a bit of some snack-food.
When the noun 茶 (cha), “tea” is joined with 子 (ko), “child” with the associative particle の (no), the result doesn’t mean “tea child” – instead it refers to 茶菓子 (chagashi), various kinds of sweets traditionally served together with (green) tea. The お (o) is just your normal honorific suffix attached to make the phrase feel “softer” and more suited to polite company. Appended to this noun phrase we have さいさい (saisai), meaningless sound-words attached to the phrase for rhythmic purposes or as a sort of encouraging noise. It’s supposedly borrowed from a folk-song that goes のんこさいさい (nonko sai sai), applied to this context due to the shared ko.
Naturally, leaving out the add-on and simply saying お茶の子 is perfectly acceptable. Emphasizing the phrase by adding 河童の屁 (kappa no he), “a kappa’s fart,” is also an option. (The latter phrase also refers to something trivial or, by extension, trivially easy.)
While the commonly-accepted explanation for this phrase’s origin is “as easy as eating a piece of candy,” an alternate explanation posits that in certain dialects, 茶の子 refers to 茶粥 (chagayu), rice gruel flavored with tea, eaten at times to start the day before the formal breakfast proper. From this, it’s argued that the phrase refers to something so simple it can be completed before breakfast. I suspect that this is a folk etymology rather than a real one, though.
(“Mainichi nijikan ijou renshuu suru koto ni shiterun da. Yappa ken-reberu no konkuuru de yuushou suru nante ocha no ko saisai to wa ikanai kara.”)
[“I’m trying to practice at least two hours every day. Taking first place at the prefecture-level competition isn’t going to be so easy as all that!”]