The authors agree that this surname is of Sicilian dialect origin and derives from a nickname based on the adjective lèggiu (with the variants lièggiu and lìggiu), which means "light, slight, inconstant". E. Rossoni notes that the term probably expressed an unflattering judgement about the founding ancestors of the line.

V. Blunda specifies that the adjective covers both physical lightness —a slender figure— and fickleness of character, so that the nickname could have been applied in either of those senses before becoming a surname.

Rossoni details the geographical distribution: the form Leggio is typically Sicilian, with a strong presence in Ragusa and records also in Palermo, Isnello, Corleone and Partinico in the Palermo area; in Santa Ninfa, Castelvetrano and Trapani in the Trapani area; in Syracuse; in Vittoria and Modica in the Ragusa area; and in Sambuca di Sicilia and Sciacca in the Agrigento area. It further shows a pocket in the Salento —the southernmost zone of the region of Puglia, in southern Italy—, with a presence in San Pietro Vernotico in the Brindisi area and in Surano and San Cassiano in the Lecce area. The variant Liggio is also Sicilian and specific to Palermo and Corleone.