Has "Takeshi" some particular significance ?

It's Takashi.

does it have any significance ?

Fixed ケ→カ. And not sure what you mean by "significance," it's a name...

Names sometimes have a meaning and very often a connotation.
That's what a significance is...

As a regular word, no, it doesn't mean anything. It's extremely common when used with name kanji, however, as it can mean secrecy, harmony, wide, expansive, rank, rock, respected officer, up, strong warrior, respected heir, strong, allotment, officer's desk, advantageous warrior, reward allotment, ascendance, extreme will, peak, desk of wills, refreshing, music, day, precious serpent, congratulated officer, obligation, congratulated history, highly esteemed motivation, fidelity, high preeminence, sacred descendent, remarkable history, principle, high officer, radiance, responsible history, sunlit history, long history, prosperous season, principal officer, ... And perhaps a few thousand more entries that probably won't fit in this comment field. But I think you can get a pretty good idea what "Takashi" can mean now. If it were to have a connotation, well... Maybe because he's supposed to be valiant in nature, according to his name, but he turns tail at ghosts? At any rate, I don't believe I can convey such a connotation in my translation. I'm welcome to suggestions, though, but frankly, translating names is extremely bad practice, so I'll refrain from doing it anyways.

>but frankly, translating names is extremely bad practice

I disagree.
I use names with connotations all the time. They should be rendered to pass as adequate translations.

Thank you for the explanations. I knew it had meaning(s). Of course it has a connotation !