テイ, ダイ, デ, おとうと, て
younger brother, faithful service to elders
JLPT4 G2 S7 F1161
The relevant bronzeware inscription form shows a cord or vine aligned with a stake, the lower part of which is represented by a slanting line → crops aligned by size → *younger brother*; *disciple* (← occupant of a lower vertical stage in a hierarchy). For a conceptually related term indicating a "younger sister," compare 娣.
[Full Kanji Etymology List]