People describe sadness as "heartache." The link between sadness and physical pain such as heartache has been empirically proven; however, the mental foundations that support the connection between sadness and pain remain unclear. The present study hypothesized that the connection between sadness and specific physical pain is established by concepts referred to as "sadness-pain concept," which are internalized based on features relating to interactions between the body and external situations. We examined the use of pain-related onomatopoeias as metaphorical words for expressing sadness, setting three primary goals for our study: (i) to identify sadness-pain words usable for both sadness and physical pains, (ii) to determine the specific sadness-pain words used for certain sadness situations, and (iii) to reveal the pain-related characteristics that are linked to such sadness situations. Sixty-nine participants were asked to rate 28 pain-onomatopoeic words in terms of the types of emotions, sadness situations, body parts, and characteristics of pain respectively. Consequently, seven words were identified as sadness-pain words. Furthermore, the specific sadness situations related to each sadness-pain word were determined. Situation-dependent sadness-pain words, for example, zukin zukin for loss, were found to be associated with specific body parts and pain properties. These findings indicate that the shared representation of sadness and physical pain as an emotional concept is based on interactions between the body and external situations.