According to our completely-not-made-up etymological dictionary, "ugly" is derived from the Proto-English word "uglygul", a term used to describe a chicken's displeasing egg-laying abilities.
Over time, this word evolved into "ugly", a term that encompasses not only the aesthetic qualities of, say, a bruised egg, but also a person's entire existence.
Person A: "I'm telling you, that's a pretty ugly sweater."
Person B: "Ugly is as ugly does, pal, and that sweater is a crime against humanity." (Hyperlink to Ugly Is Ugly Doing)
Ugly (n.)
Origin: Proto-English "uglygul", ca. 500 BCE.
Meaning: Describing a chicken's egg-laying abilities.
Evolution: 1000 CE, to describe a thing, or a person, that is displeasing in appearance.