I
• БОГ <ГОСПОДЬ, АЛЛАХ> (ЕГО <тебя и т.п.> ЗНАЕТ <ВЕДАЕТ>; БОГ ВЕСТЬ{{}}all coll
[VPsubj; these forms only; usu. the main clause in a complex sent or indep. sent; fixed WO]
=====
⇒ no one knows, it is impossible (for s.o.) to know:
- God <(the) Lord, heaven, goodness> (only) knows;
- God alone knows.
♦ "Кто же я таков, по твоему разумению?" - "Бог тебя знает; но кто бы ты ни был, ты шутишь опасную шутку" (Пушкин 2). "And who am I then, in your opinion?" "God only knows; but whoever you may be, you're playing a dangerous game" (2a).
♦ ...Он ездит и в свет, и читает: когда он успевает - бог весть (Гончаров 1). ...There was his social life and his reading-heaven only knows how he found the time! (1b).
♦ Родители его были дворяне, но столбовые или личные - бог ведает (Гоголь 3). God alone knows whether his parents, who were of the nobility, were so by descent or personal merit (3d).
II
[VPsubj; these forms only; fixed WO]
=====
1. [usu. the main clause in a complex sent; when foll. by an Adv, may be used as adv]
⇒ no one knows (who, what, how etc):
- God <(the) Lord, heaven, goodness> (only) knows (who <what, how etc>).
♦ Выкопали всё, разузнали его [Чичикова] прежнюю историю. Бог весть, откуда всё это пронюхали... (Гоголь 3). Everything was dug up and all the past history of his [Chichikov's] life became known. God only knows how they got on the scent of it... (3a).
♦ Бог весть, почему нервничали встречавшие (Свирский 1). Heaven knows why the reception party should have been so nervous (1a).
♦ Дом Обломовых был когда-то богат и знаменит в своей стороне, но потом, бог знает отчего, всё беднел, мельчал... (Гончаров 1). The Oblomov family had once been rich and famous in its part of the country, but afterwards, goodness only knows why, it had grown poorer, lost all its influence... (1a).
2. [used as NP (when foll. by кто, что), AdjP (when foll. by какой), or AdvP (when foll. by где, куда etc)]
⇒ used to express a strong emotional reaction-anger, indignation, bewilderment etc:
- God <(the) Lord, heaven, goodness> (only) knows (who <what, how etc>)!;
- what sort <kind> of (a) [NP] is he (she, that etc)!;
- [in limited contexts;
- said with ironic intonation] some [NP] (I must say)!
♦ "Да ведь она тоже мне двоюродная тётка". - "Она вам тётка ещё бог знает какая: с мужниной стороны..." (Гоголь 3). "But, you know, she is a cousin of mine." "What sort of a cousin is she to you...only on your husband's side..." (3d).
Большой русско-английский фразеологический словарь. — М.: ACT-ПРЕСС КНИГА. С.И. Лубенская. 2004.