Where does “ความตั้งใจ” come from?

ความตั้งใจ (Thai) comes from Thai ตั้งใจ, from Thai ใจ, from Proto-Tai cɤɰᴬ — heart; breath.

Ancestry of “ความตั้งใจ”, step by step

ความตั้งใจ traces back through two separate lines of ancestry.

via Thai ตั้งใจ

StepLanguageWordMeaning
1Thaiตั้งใจto be mindful, attentive, or heedful; to attend; to pay attention; to heed
2Thaiใจheart; mind; spirit; breath
3Proto-Taicɤɰᴬheart; breath

via Thai ความ

StepLanguageWordMeaning
1Thaiความaffair; matter; content; essence; subject;...
2Proto-Taiɣwaːmᴬmatter
Every word from Proto-Tai cɤɰᴬ →Every word from Thai ใจ →Every word from Thai ตั้งใจ →