طَوِيلُ النِّجَادِ
Having a long sword-strap; figuratively, a tall person.
Al-nijad denotes a sword-strap. A tall wearer may require a comparatively long strap, allowing the expression to indicate stature. The intended meaning is an attribute of the person, not merely a technical description of a sword.
If the person really has a long strap, that does not invalidate the kinayah. The literal possibility is deliberately retained.