It's in reference to tides; spring tides happen just after every full and new moon, meaning the tides are larger, while neap tides occur after first quarter and third quarter moon, meaning the tides are smaller.
zmaj 🤓3:24 · 2024-03-01T21:25:26.048Z
"Spring" and "neap" refer to tides that occur at particular phases of the moon. Spring tides occur every new and full moon, while neap tides occur every first and third quarter.