dyed-in-the-wool

adjective2

1. •
   Having the fibres dyed before they are formed into cloth.

   • […] some Druggets with Thread, that are dyed in the Piece; the others are dyed in the Wool, i. e. the Wool of which they are made, is dyed of several Colours, before it is carded, spun, and weaved. — 1747
2. •
   (figurative) Firmly established in one's beliefs or habits; having a specified characteristic, identity, etc. deeply ingrained in one's nature.

   • Smith was a dyed-in-the-wool typist and never really got used to writing on computers.
   • John Major was described by his opponents as a dyed-in-the-wool Conservative.