Why holiday detector is called so?

Answer 1

Following the description of the pronunciation problem, it is helpful to understand this widely used quality control process.

Briefly, this process involves testing the integrity of a non-conductive surface such as painted coatings or plastic by attempting to pass an electric pulse between electrodes, each applied to either side of the surface. If any holes or gaps exist, then the electricity is able to complete a circuit sounding a warning, which alerts the operative to the existence of a fault. Hence the specialised term 'Zap Test' used in some industrial settings.

The word 'holiday' in this industrial or manufacturing connection might seem an unusual choice of word and most dictionaries only include the traditional and wider known uses. According to Chambers dictionary of etymology, the term, possibly recorded before the 1200's developed from the old English hālig dæg a religious term, literally meaning a 'Holy Day'. Another form was Hallowmas, apparently in use until the 16th century.

Searches of the BNC and Collins Cobuild Corpora didn't yield any industrial uses, so it required a manual search of the full and Shorter OEDs in the local libraries in Canterbury and Whitstable to find reliable sources of variants:

The OED lists the following examples (among many others) of the noun 'holiday' :

1. Holiday (n) A consecrated day; a religious festival.

2a ~ A day on which ordinary occupations ( of an individual or a community) are suspended; a day of exemption or cessation from work; a day of fasting, recreation or amusement.

2e a holiday Used euphemistically for imprisonment. e.g. 'a little holiday'.

~ colloquial: nautical: A spot carelessly left untreated in tarring or varnishing. 1785 Grosse Dict Vulg T s.v : 'A holiday is any part of a ship's bottom left uncovered in painting it.'

~ 1882 Holidays, parts left untouched in dusting 'Don't leave any holidays'.

It is in these latter examples that the idea of missing a piece of work or 'taking a holiday from' an area or section of work is conveyed.

Likewise, the Shorter OED 2002 Ed. describes the term in this context as being 'chiefly nautical - A patch or area unintentionally left in painting etc.

Similarly, According to PK Kemp (1976):

Holiday - a gap unintentionally left uncovered when painting or varnishing on board ship and applying equally to a ship herself or to her masts and spars. It is also a gap left, equally unintentionally in paying a deck seam with oakum and pitch.

http://www.hltmag.co.uk/jun09/less03.htm