The phrase comes from Brazilian Portuguese slang, where memo is a casual spoken shortening of mesmo and cachorro is used playfully between friends rather than as a literal reference to a dog. Short voice clips in this style spread widely through WhatsApp groups and Brazilian meme pages, where they are reused as ready-made reactions. This one survives because the wording is instantly quotable, works without visual context, and can signal agreement, pride or playful confidence in under two seconds, making it easy to drop into chats, edits and livestreams.