low, short
矮 centers on being physically low in height: short or squat. The meanings "low" and "short" both describe a lack of vertical extent.
矮 combines 矢 (arrow) and 委, which likely contributes the sound. The arrow component may relate to measuring or shortness, but the exact historical development is uncertain.
An arrow 矢 beside a bent-over woman 委 suggests something short: imagine an arrow that is too short to reach its target, or a woman who is short in stature.
For ワイ, imagine a short person asking "Why?" in a high-pitched voice: "Why?" sounds like ワイ, and the short stature makes the question seem even smaller.
diminutive; dwarfish; pygmy; stunted; undersized
dwarf star
(Japanese) bantam
white dwarf
dwarf
dwarf irregular galaxy
reduction (in size); shrinking; minimization
dwarf galaxy
micropenis
dwarfism
dwarf planet
low or short tree
small stature
petty spurge (Euphorbia peplus)
Chamaecyparis obtusa var. breviramea (ornamental variety of hinoki cypress)
brown dwarf
red dwarf
black dwarf