The ⚀trina·lengthel, or ⚀thumb·length
The ⚀trina·lengthel, or three ⚀morsels, is a close approximation of the TGM uncia·Grafut, the first negative power of the Grafut. This also makes it a close approximation of a USC inch. (It is exactly 31/32d|0.Ɛ76z USC inch.)
The English word inch is derived from Latin uncia, "one twelfth", since the inch is a twelfth of the foot (Latin pes), and the foot is a basic unit of length in customary measures. Similarly, the TGM uncia·Grafut is by definition a twelfth of the Grafut, and the Grafut is the basic unit of length in TGM. So colloquializing that as a "Gravity inch" or "Gravinch" would be appropriate.
However, Primel does not colloquialize the ⚀trina·lengthel as a kind of "inch", because it is not the uncia of a basic Primel length unit; it is three times the basic unit, the ⚀lengthel. Instead, Primel notes the fact that languages other than English have used their word for "thumb" as the name for such a unit. For example: Latin pollex, Italian pollice, French pouce, Spanish pulgada, Portuguese polegada, Catalan polzada. Consequently, a suggested colloquial name for the ⚀trina·lengthel is the ⚀thumb·length. Alternatively, the ⚀pollical·length is suggested.