The thin end of the wedge British negative adverb phrase
This phrase is used when you talk about a bad matter, despite of its harmlessness, you fear it will slowly develop into something more serious and harmful.
This phrase indicates that something which initially seems bad but harmless can become much worse in the future or lead to a harmful development.
Those pharmacies have put the price of face masks up. It'll be the thin end of the wedge, if others follow along.
This law will be the thin edge of the wedge, if it's passed. People' liberties can be restricted.
hurt someone or yourself
Completely developed, trained or qualified
One's advantage due to their extraordinary skill, ability, or resources.
This phrase is put behind verb (be) to support the subject mentioned.
Fastfood is the thin end of the wedge, despite of its convenience, it'll take a toll on our body for a long time.
This phrase dates back to the mid-19th century, it referres to the thin or pointed end of the wedge. Wedge like this is often made from metal or wood and is used as axe blade. With the thin end, it can be used to slowly divide object into pieces, hence its meaning of something may has little importance but can cause serious development later on.