Where does “mýdlíčko” come from?

mýdlíčko (Czech) comes from Czech mýdlo, from Proto-Slavic mydlo, from Proto-Slavic -dlo, from Proto-Indo-European -dʰlom — Alternative form of *-trom; instrumental suffix;...

Ancestry of “mýdlíčko”, step by step

Step	Language	Word	Meaning
1	Czech	mýdlo	soap
2	Proto-Slavic	mydlo	soap
3	Proto-Slavic	-dlo	Forms nouns denoting a tool or instrument
4	Proto-Indo-European	-dʰlom	Alternative form of *-trom; instrumental suffix;...

Every word from Proto-Indo-European -dʰlom →Every word from Proto-Slavic -dlo →Every word from Proto-Slavic mydlo →