Alcanzar (“to reach”, in the sense of “to achieve” such as, reaching a goal) comes from the Latin prefix in– with the Latin calx meaning, limestone. Limestone? Huh?
The word for Limestone became the word for achieving because, quite simply, you need to step on it to get a bit higher, to be a bit closer to the stars. Think of the word reach itself — there is a literal sense of holding your hand a bit higher, a bit further, so you can get to something. A bit like stepping on a stone. But there is the metaphorical sense of both words, reaching a goal.
From the root calx, we also get the English… calcium. Calcium is just another really hard substance that looks just like limestone.
You know another hard substance that looks like limestone? Chalk. And yes, chalk comes from calx, too!