Regrettable means to be wished otherwise. Something happened, and everybody would prefer it had not.
It is one of the great words of official evasion, since calling an event regrettable acknowledges it without accepting responsibility for it, and readers hear that immediately. A regrettable incident is a formula. The adverb regrettably introduces bad news politely. It is worth keeping apart from regretful, which describes a person feeling regret rather than a thing deserving it.
1adjectiveregrettableGiving cause for regret.
“The whole episode was deeply regrettable.”
Old French
regreter
Middle English
regretten
English
regret
English, today
regrettable
Built from
From regret + -able. regret comes from Middle English regretten, from Old French regreter, from und + re-. From Middle English regretten, regreten, from Old French regreter, regrater (“to lament”), from re- + greter, grater (“to weep”), from Frankish grātan (“to weep, mourn, lament”), from Proto-Germanic grētaną (“to weep”), from Proto-Indo-European ǵʰreh₁d- (“to sound”); and Frankish greutan (“to cry, weep”), from Proto-Germanic greutaną (“to weep, cry”), from Proto-Indo-European gʰrewd- (“to weep, be sad”), equivalent to re- + greet. Cognate with Old High German grāzan (“to cry”), Old English grǣtan (“to weep, greet”), Old English grēotan (“to weep, lament”), Old Norse gráta (“to weep, groan”), Gothic 𐌲𐍂𐌴𐍄𐌰𐌽 (“to weep”). More at greet.
Etymology from Wiktionary, CC BY-SA