Proto-Indo-European *keh₂u- "to burn" became Greek καίω kaiō "to burn" and καυστός kaustos "burnt, burnable". ὁλόκαυστος holokaustos meant "burnt whole", from ὅλος holos "whole". Borrowed into Latin as holocaustum, it originally meant "a whole burnt offering".
The related word ἐγκαίω egkaiō meant "to brand, paint with encaustic" - encaustic being a process of painting with wax and fixing the colours with fire. ἕγκαυστον egkauston was the ink used in the signature of Greek and Roman emperors - this was borrowed into Latin as encaustum, which developed into Old French enque, borrowed into English as ink.