Source

File: wp-includes/class-wp-query.php

protected function get_search_stopwords() {
		if ( isset( $this->stopwords ) ) {
			return $this->stopwords;
		}

		/*
		 * translators: This is a comma-separated list of very common words that should be excluded from a search,
		 * like a, an, and the. These are usually called "stopwords". You should not simply translate these individual
		 * words into your language. Instead, look for and provide commonly accepted stopwords in your language.
		 */
		$words = explode(
			',',
			_x(
				'about,an,are,as,at,be,by,com,for,from,how,in,is,it,of,on,or,that,the,this,to,was,what,when,where,who,will,with,www',
				'Comma-separated list of search stopwords in your language'
			)
		);

		$stopwords = array();
		foreach ( $words as $word ) {
			$word = trim( $word, "\r\n\t " );
			if ( $word ) {
				$stopwords[] = $word;
			}
		}

		/**
		 * Filters stopwords used when parsing search terms.
		 *
		 * @since 3.7.0
		 *
		 * @param string[] $stopwords Array of stopwords.
		 */
		$this->stopwords = apply_filters( 'wp_search_stopwords', $stopwords );
		return $this->stopwords;
	}