Interesting but NMS

Ostadar is one of the few names relating to rainbows that is definitively masculine in its original language. Beyond its lovely meaning, Ostadar has a fabulous ring to it and is ripe for greater use outside of the Basque region of Spain.

Variously spelled Swithun or Swithin, and associated with St. Swithin's day, July 15th, which is famous as a weather predictor a la Groundhog's Day: supposedly, the weather on his feast day will continue for 40 days. This would certainly make a unique choice.

Uzziah was an Old Testament king of Judah, among other personages. The initial U is a bit funky for modern tastes; we don't see this one enjoying a revival ala Isaiah and Noah anytime soon.

Is Keela distinct enough from Kayla to sound fresh and new? Maybe, though its similarity to the trendy cluster of names that also includes Kaylie and Kylie and Kelly may be enough to turn you off. Keela, a relative of the less serious Keely and the male Keelan, is used in modern Ireland.