rud·dle 
(rŭdl) also red·dle (rĕdl) or rad·dle (rădl)
(rŭdl) also red·dle (rĕdl) or rad·dle (rădl)n.
Red ocherous iron ore, used in dyeing and marking.
tr.v. rud·dled, rud·dling, rud·dles also red·dled or red·dling or red·dles or rad·dled or rad·dling or rad·dles
To dye or mark with or as if with red ocher: ruddle sheep.
[Probably diminutive of rud, red, from Middle English rudde, from Old English rudu; see reudh- in the Appendix of Indo-European roots.]