touch wood

Touch wood — плюнь через левое плечо, постучи по деревяшке; тьфу-тьфу-тьфу чтоб не сглазить

Usage: A catchphrase used to avert bad luck by touching wood (jocularly one's head), especially to avoid misfortune as a result of boasting (of one's good fortune, success, etc.) or wishing for something.

Example: "Have you ever been to hospital?" "No, touch wood." — (Типун тебе на язык), плюнь через левое плечо. Постучи по деревяшке. /Тьфу-тьфу-тьфу чтоб не сглазить.

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It is a vestige of an old superstition that certain trees had a sacred significance and would give blessing and protection if touched - a notion that may have its origins in the cult of Pan, a Greek god of nature. Alternatively the expression may date from medieval times when relics, including pieces reputed to be from Christ's cross, were hawked around, to be bought or touched for a blessing.

see also
[knock on wood]
[сглазить]