Currently, the descriptions of blocks in the parts library currently reflect the native language of whomever contributed the shapes. For instance many of the electrical symbols have Japanese names because the person contributing the symbols was from Japan and used a Japanese edition of the relevant international standard.
This is very impractical, since only a minority of 5% to 10% of QCad users are likely to understand Japanese. While there is no worldwide language understood by everybody, using the language of the QCad default user interface (which happens to be English) is much more likely to be understood by QCad users worldwide, even those not from an "English-speaking" country.
[Statistical note: the population of Japan is slightly less than 5% of the world population, and few people outside Japan read Japanese, 10% of the world population would be a high estimate. Countries that use English as (one of) their official language(s) include England, India, Pakistan, Canada, Australia, South Africa, USA and many other former English colonies, totalling more than 20% of the world population. Add to this the many countries where English is taught as a second language (like my own country) and the many "western" languages where the words are similar to those in English (e.g. German, French, Spanish, Italian, Nordic languages etc.) and the number of people capable of at least recognizing English names of familiar technical terms grows to about half the world population.]