For some reason best known to himself - Idioms by The Free Dictionary
for a/some reason/reasons best known to himself, herself, etc. (redirected from for some reason best known to himself)
for (a/some) reason(s) best known to (oneself)
For strange or perplexing reasons that the speaker cannot understand. For reasons best known to herself, Mom refuses to wear her glasses and goes around squinting at everything instead.
for reasons best known to himself (or herself, etc.) used when recounting someone's behaviour to suggest that it is puzzling or perverse. chiefly humorous
for a/some reason/reasons best known to himˈself, herˈself, etc. (humorous) for a reason or reasons which other people find hard to understand: For reasons best known to himself, he wears two pairs of socks.
References in classic literature
Knightley, who, for some reason best known to himself
, had certainly taken an early dislike to Frank Churchill, was only growing to dislike him more.
Lawrence had been invited to join us, but, for some reason best known to himself
, had refused to give us his company.