Popularly means “by most people” or “in the way most people say or think.” It often sits in phrases like popularly known as and popularly believed. Those do not mean the idea is fashionable, or that you personally like it; they mean this is the common name or the common belief, which may even be wrong. The -ly here is the ordinary adverb ending, turning popular toward how the many behave or speak, not toward style. Though actually, students who know popular as “liked by many” sometimes hear popularly as “in a trendy way.” That reading is rare.

普遍地；一般（所稱／所信）