Rows or levels of a structure arranged one above another. Hierarchical levels or ranks within a system or organization.
From Old French tire 'row, rank', from tirer 'to draw, pull'. Originally referred to the arrangement of archers in ranks. The architectural sense developed from military formations. The word entered English in the 15th century, evolving from military to general hierarchical usage.
The word 'tier' comes from archery formations, where archers were arranged in rows that could 'draw' and fire in sequence. This military origin explains why we still use 'tier' to describe hierarchical systems - each level has its turn to act, just like archers in formation.
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