Your eyes—deep wells of blueness Reflect the steady flame That is your gentle spirit, Is Constancy your name? For always it burns brightly: The candle that is you! No harsh wind sways to dimness This light so ever true.
Someone is being praised here, and the speaker pays the compliment in a single sustained image: a steady flame. It starts with the beloved's eyes, described as deep blue wells, and what those wells reflect is a burning light, which the speaker takes to be the person's gentle spirit. That leads to a playful question, "Is Constancy your name?", as if the person were so reliable that the word itself could be a name. The title makes the same point.
The second half turns the flame into a candle and adds a threat: wind. But no harsh wind can dim it. The speaker admires a person who stays warm and unchanged whatever happens around them. The mood is tender and admiring, even a little hushed, and the short lines and regular rhymes (name/flame, you/true) give it a calm, dependable rhythm that mirrors the loyalty it describes.