Where "órale" comes from
Órale comes from Mexican Spanish. The most common explanation is that it grew out of "ahora" ("now"), shortened and softened, with the "-le" ending seen in other Spanish exclamations like "ándale." That would make the original sense something like "right now!" or "let's go!" This is the leading theory, but nobody has documented each step of the change, so treat it as a well-supported guess rather than settled fact.
Over time the word stretched. Depending on tone and context, "órale" can mean "alright," "okay," "come on," "wow," or even a skeptical "really?" Mexican speakers use it across the country, and it became a familiar part of everyday speech in Mexican-American families and neighborhoods. In Los Angeles, where Mexican and Chicano communities are large and long-established, it became a staple of Chicano speech and Spanglish, often mixed with English around it.
Some writers have proposed other sources for the word, but none has strong support, so the "ahora" link remains the standard account. The exact route, and the date it first appeared in writing, are not firmly documented.