name of an ancient tribe
氐 is a rare kanji that primarily refers to the name of an ancient tribe. Its standalone meaning is narrow and historical, with no clear broader conceptual center beyond that specific reference.
The historical origin of 氐 is uncertain. It may have originally depicted a low foundation or base, but its use as a tribal name is the primary surviving meaning.
Think of 氐 as a clan emblem: the top 氏 suggests a family or clan, and the bottom dot marks it as a specific ancient tribe.
For テイ, imagine an ancient tribal chief named Tay who leads the 氐 people: Tay -> テイ.