You can think of a vassal as someone to hand over his freedom and standing up holding a piece of land. Both halves matter: he gets something real to live on, and he gives up the right to choose. Every later use of the word keeps that trade — protection and resources coming down, loyalty and obedience going up.
From the word’s history
Wiktionary traces it through Old French vassal and Medieval Latin vassallus (manservant, retainer) to Latin vassus (servant), from Gaulish *wassos (young man, squire) — the picture throughout is of a young man attached to someone else's household.
來源資料把這個字一路追到古法文 vassal、中世紀拉丁文 vassallus（僕從、隨從）、拉丁文 vassus（僕人），再到高盧語 *wassos（年輕人、侍從）。從頭到尾的畫面都是「跟在別人身邊做事的年輕人」。
Wiktionary (kaikki) entry for 'vassal' supplied in the evidence packet (source_ref kaikki:3f6f69a190036ae4:672308107:23388)
登入就可以看每一支怎麼連回核心畫面。