The most probable etymology derives it through aphaeresis (an abbreviated form with the suppression of the initial syllable) from hypocoristics (affectionate diminutive forms) of the medieval name Costante or Costantino (Italian from the Latin Constans, constantis, "firm, persevering"), widely documented in medieval Italian onomastics for its Christian auspicious and devotional value.

The evolutionary chain would be:

Costantuccio or Costantucci (affectionate diminutive) → Stantucci → Tantucci.

The double diminutive plural suffix -ucci (a combination of the diminutive suffix -uccio characteristic of central and southern Italy) has an affectionate value and originally designated the small descendants of the clan or the younger members of the Costanti family.

An alternative hypothesis relates it to the Italian and dialectal adjective tanto ("much, abundant", from the Latin tantus), applied as an affectionate-ironic byname to a person characterised by their exuberance or their prominent stature, with a descriptive value.

The distribution of the surname is limited and is concentrated probably in central Italy, especially in the Marche and Umbria, the areas of greatest diffusion of the suffix -ucci.

This surname does not appear as an autonomous entry in the classical Italian onomastic repertories consulted, so the proposed etymology must be considered indicative.