One of the proposed names for it during development was Lohlee. It was also originally a Water/Psychic type.
Lore Time! Laslee and Wifemin were Fochun exclusive, but as Chezetta and Mozzamazel overtook they migrated to Ebin Isles, but even that wasn't enough to get away from the cheese pizza as they invaded their home there too. Female Chezetta and Mozzamazel were more chosen frequently over Lasslee and Wifemin, so natural selection shifted their gender of 50/50 to 7/1 in favor of the males.
Lasslee is based off of the lolita (AKA loli) character archetype, which is a seductive young (or young-looking) girl. Its wide-eyed expression and teeth resembling that of a chipmunk are a reference to the artstyle of Pokemon characters that was adopted in Generation 6 and beyond, occasionally referred to as "Shaunaface" by some fans. Its predominately male gender ratio in spite of its feminine appearance is a reference to the term "trap", referring to homosexual men who dress as women in order to have intercourse with heterosexual men.
Lasslee is a combination of lass and a corruption of loli.