insole

[ in-sohl ]
/ ˈɪnˌsoʊl /

noun

the inner sole of a shoe or boot.
a thickness of material laid as an inner sole within a shoe, especially for comfort.

Origin of insole

First recorded in 1850–55; in + sole2
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for insole

insole

/ (ˈɪnˌsəʊl) /

noun

the inner sole of a shoe or boot
a loose additional inner sole used to give extra warmth, comfort, etc
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012