The phrase "at least" is used to indicate a minimum amount, degree, or requirement. It implies that the mentioned quantity is the lowest acceptable level, and there may be more but not less than that. It is often used to provide reassurance or to express a positive point in a situation that may otherwise seem negative.
The phrase "at least" stems from Middle English, combining "at," meaning "in the position of" or "during," with "least," which is the superlative form of "little," meaning the smallest or the minimum degree of something. This combination suggests a position or state of being that is not lower than the indicated level.