The story
Alteration of LGBT, where L is reinterpreted as the Spanish plural definite article los, and GBT as a noun, + -ies (plural suffix). Popularized by Puerto Rican TikTok influencer Dez the Lez in a short storytime video on 1 June 2021, the start of Pride Month. In the video, the creator explains how her Spanish-speaking mother created the term as a nonce word after forgetting the correct term in English.
Etymology from Wiktionary, CC BY-SA 4.0.