Hirt's law or Hirt–Illich-Svitych's law, named after Hermann Hirt, who originally postulated it in 1895, is a Balto-Slavic sound law that triggered the retraction of the accent under certain conditions. Wikipedia

Balto-Slavic accent-retraction sound change Wikidata

A Balto-Slavic sound law stating that the inherited Proto-Indo-European stress would retract to a non-ablauting pretonic vowel or a syllabic sonorant if it was followed by a consonantal (non-syllabic) laryngeal that closed the preceding syllable. Wiktionary