means A device or enclosure that rains water down on you for washing, or the act of getting clean under it — and by extension a brief fall of rain or a party where gifts pour onto the guest of honor.

from From Old English 'scūr,' meaning a brief fall of rain, hail, or even arrows — anything that comes down in a sudden burst. It has cousins across the Germanic family (German 'Schauer'). The bathing fixture is a much later twist: the 'shower bath' arrived only in the 19th century, borrowing the idea of falling water. The gift-giving 'baby shower' or 'bridal shower' is later still, an early-20th-century American notion of presents raining down on the lucky recipient.