The term is based on "sword lesbian", a humorous label not rooted in exclusion for lesbians whose weapon of choice is a sword. A longsword is used specifically for the alliteration. The weapon takes on additional meaning with this identity, signifying intent to "defend" the label from anyone who isn't a binary woman using she/her pronouns exclusively attracted to women.
A tweet by Twitter user missyxthirteen indicates that the primary flag was created by now-deactivated Instagram user flop._.shop on or before June 27, 2020. The tweet also provided the significance of the flag's seven stripes. From top to bottom, the colors represent being against he/him, they/them, and neopronoun lesbians; the "purity" of lesbianism; exclusive attraction to women; the safety felt around others with she/her pronouns; and the label only being applicable to binary women.
Longsword lesbians exclude PNC lesbians through the belief that pronouns strictly indicate gender. However, lesbianism has long been associated with gender nonconformity and experimentation. Many languages exist that lack gender-specific pronouns, making the claim not universally applicable.
Longsword lesbians mandate that a lesbian must be a binary woman attracted exclusively to binary women. Traditionally, this definition has been used by dictionaries, such as the Oxford English Dictionary, which defines a lesbian as a homosexual woman. This is the most common use of the word, but definitions are not dictated by dictionaries, and definitions are not unchanging facts.