Primitive elvish
yon
root. son
yon
root. wide, extensive
yondō
noun. son, boy
ent
adverb. over there
gardā
noun. region
yad
root. wide
yon
root. son
yon
root. wide, extensive
yondō
noun. son, boy
ent
adverb. over there
gardā
noun. region
yad
root. wide
This root was the basis for Elvish “son” words for much of Tolkien’s life. The earliest indications of this root are ᴱQ. †Y̯ó (or y̯ond-) “son” and ᴱQ. yondo “male descendant”, both tied to the patronymic suffix ᴱQ. -ion “son of, descendant of” appearing in many names (QL/106). In the contemporaneous Gnomish Lexicon there was also the related patronymic prefix G. go- (GL/40), which implies the existence of a root ✱ᴱ√YO(NO) since [[g|initial [j] usually became [g]]] in Gnomish. However, go- was deleted and changed to G. bo-, along with new Qenya forms ᴱQ. vô and ᴱQ. vondo (GL/23, 40), implying a change to a root ✱ᴱ√VO(NO).
In Early Noldorin Word-lists from the 1920s, ᴱN. gó “son” reappeared along with ᴱQ. ion and yondi (PE13/144). In The Etymologies of the 1930s the root appeared as ᴹ√YŌ or ᴹ√YON “son” with derivatives like ᴹQ. yondo/N. ionn “son” and patronymic -ion (Ety/YŌ). However, in notes labeled “Changes affecting Silmarillion nomenclature” from the late 1950s, Tolkien wrote “Delete entirely yondo = ‘son’! Very unsuitable” (PE17/43). This particular note was rejected when Tolkien changed √YON “wide, extensive” to √YAN (PE17/42). Other notes in the same bundle indicate Tolkien was still seeking a new word for son, saying “Q wanted: son, daughter”, though yon(do) remained among the forms he was considering (PE17/170, 190).
However, it seems Tolkien eventually stopped vacillating and restored √YON, since the patronymic -ion was never discarded, and yon- was the basis for “son” words in notes from the late 1960s (VT47/26).