Lapalissade

A lapalissade is an obvious truth—i.e. a truism or tautology—which produces a comical effect. It is derived from the name Jacques de la Palice, and the word is used in several languages.
Origin.
La Palice's epitaph reads
These words were misread (accidentally or intentionally) as "...il ſerait [serait] encore en vie" ("...he would still be alive"), where the long s aids in the confusion. In the 16th century this misreading was incorporated into a popular satirical song, and in time many other variants developed, including "... que deux jours avant sa mort / il était encore en vie" ("... that two days before his death / he was still quite alive") and "... et quand il était tout nu, / il n'avait point de chemise"
("... and when he was stark naked / he didn't wear a shirt").
In the early 18th century Bernard de la Monnoye collected over 50 of these humorous "La Palice" quatrains, and published them as a burlesque "Song of La Palice". From that song came the French term "lapalissade" meaning an utterly obvious truth—i.e. a truism or tautology, and it was borrowed into several other languages. Since that day, when you say something very obvious, your interlocutor answers: "La Palice would have said as much!" (in French: "La Palice en aurait dit autant!").
Similar terms.
In Spanish culture, an analog is a folkloric character (Perogrullo) with his "perogrulladas": "Verdad de Pedro Grullo, que a la mano cerrada, la llama puño" (The truth of Pedro Grullo, when his hand is closed, he calls it a fist).
In English, one might reference "Captain Obvious" as having spoken a self-evident truth. Other kinds of trite expressions are "platitude" and "bromide".