Stony-hearted

The phrase is first recorded in 1569, in Thomas Underdown’s translation of the Æthiopian History of Heliodorus:

” There is no man so stoany harted, but he shal be made to yeelde with our flatteringe allurmentes.”

Shakespeare picked it up and used it in Henry IV Part I , 1597

FALSTAFF
I am accursed to rob in that thief’s company: the rascal hath removed my horse, and tied him I know not where. If I travel but four foot by the squier further afoot, I shall break my wind. Well, I doubt not but to die a fair death for all this, if I ‘scape hanging for killing that rogue. I have forsworn his company hourly any time this two and twenty years, and yet I am bewitched with the rogue’s company. If the rascal hath not given me medicines to make me love him, I’ll be hanged; it could not be else: I have drunk medicines. Poins! Hal! a plague upon you both! Bardolph! Peto! I’ll starve ere I’ll rob a foot further. An ’twere not as good a deed as drink, to turn true man and to leave these rogues, I am the veriest varlet that ever chewed with a tooth. Eight yards of uneven ground is threescore and ten miles afoot with me; and the stony-hearted villains know it well enough: a plague upon it when thieves cannot be true one to another!