எடுத்தோம் கவிழ்த்தோம்

It can be slightly critical, but it's not a swear word. It's more like a friendly warning or a common observation of a mistake.

No. It almost always implies that the lack of thinking was a bad thing, even if the result wasn't a total disaster.

Many Tamil idioms use the first-person plural to sound more general or to reflect a shared human experience of making mistakes.

Rarely. It's better suited for dialogue, stories, and informal articles.

The opposite is 'நிதானமாக' (Nidhanamaga - calmly/deliberately) or 'யோசித்து' (Yosithu - after thinking).

No, that would be 'Vegamaga' (fast). This phrase requires a lack of planning.

No, it is purely secular and rooted in daily household and market activities.

Yes, though they might have other local variations, the core idiom is understood across the Tamil-speaking world.

You can say 'அவன் ஒரு எடுத்தோம் கவிழ்த்தோம் பேர்வழி' (Avan oru eduthom kavizhtthom peruvazhi).

Yes, it's very common to describe ending a relationship without talking it through.