comest
The word "comest" is a Latin verb form. Specifically, it is the second-person singular present active indicative of the verb "comedere". "Comedere" translates to "to eat" or "to consume" in English. Therefore, "comest" literally means "you eat" or "you consume". This form would be used in a sentence where the subject is "you" (singular) and the action is currently happening.
Latin verbs, like those in many other languages, conjugate to indicate person, number, tense, mood, and voice.
While "comest" is a direct translation and grammatically correct in Latin, its usage in modern English is